The present invention relates to semiconductor (integrated circuit) devices, and more particularly, to methods of manufacturing a semiconductor device including doping a silicon layer.
In general, semiconductor materials may be classified as single crystal, polycrystal and amorphous. A single crystal material is a material formed of a one crystal structure, a polycrystal material is a material formed to have a multi-crystal structure, and an amorphous material is a material formed of an irregular atom array, not a crystal structure.
A polycrystal generally has plural crystal structure with many grain boundaries. Such grain boundaries may interfere with movement and control of carriers, such as an electron, a hole or the like As such, an electrical characteristic if such a structure may be degraded.
A single crystal has a single crystal structure that generally has almost no grain boundary. Thus, this structure may not influence the movement and control of carriers and may provide improved electrical characteristic as compared with the polycrystal structure. In a semiconductor device including a thin film transistor (TFT) or the like having a stack structure and/or in a semiconductor device including a multilayer structure, such as a system on chip (SOC) or the like, a channel layer may be formed of single crystal material, and a single-crystal silicon thin film is generally used as a thin film to form the active area.
A method for forming a single-crystal silicon thin film is described in U.S. Pat. No. 5,972,105.
In some known methods of forming a single crystal thin film, an insulation layer pattern having an opening is formed on a single crystal substrate and a seed thin film of single crystal structure is formed in the opening through a selective epitaxial growth. An amorphous silicon thin film is then formed on the insulation layer pattern having the seed thin film and a heat treatment is performed on the amorphous silicon thin film. As a result, the amorphous silicon thin film has a phase change from the heat treatment, which changes the amorphous silicon thin film into a single-crystal silicon thin film.
The heat treatment is generally performed using a laser beam. The laser beam is projected onto the amorphous silicon thin film to heat the amorphous silicon thin film and change the amorphous silicon thin film into a single-crystal silicon thin film through a phase change. This may be referred to as laser induced epitaxial growth (LEG).
When a laser beam is irradiated onto the amorphous silicon thin film, protrusions are typically formed on the surface of the silicon at a crystallizing time, as a result of which an ablation defect, where a thickness of the thin film becomes excessively thinned, may occur between the protrusions.
FIG. 1 illustrates an image of an ablation defect measured on the surface of a single-crystal silicon thin film formed using conventional LEG. As shown in FIG. 1, the ablation defect of excessively thinned film is formed on the silicon thin film crystallized by the LEG. In such an ablation defect portion, a state of face is not even and devices typically cannot be formed thereon. Further, in forming the device, a defect may occur and a rapid drop of yield may be caused. Thus, both an increase of error occurrences on products may be caused and productivity may be lowered.